Buttonholes are made in fabrics by binding the edges of a slit in the fabric. The slit is long enough to pass the button edgewise, but not so long that the button can be pulled through it when its wide face is in contact with the fabric. Buttonholes generally are made with sewing machines by providing a binding with a zigzag stitch, after which the fabric is slit between side-by-side binding. The stitch is readily regulated by setting the sewing machine, and a simple and inexpensive buttonhole attachment can be used to hold the fabric flat and to guide the needle along a straight path to produce an even and straight binding for the buttonhole.
Buttonhole attachments usually include two elements. One element is movable with respect to the sewing machine but fixed with respect to the fabric, and the other element is fixed with respect to the sewing machine but movable with respect to the fabric. The elements move with respect to each other by having the element that is movable with respect to the fabric riding in side rails formed in the element that is fixed with respect to the fabric.
When preparing a buttonhole, one usually measures the length of the button and marks a line on the fabric that is 1/8-inch longer than the button diameter. After the fabric is marked, the buttonhole attachment is placed so that the mark will appear in a slot in the bottom of the buttonhole attachment. The sewing machine is then operated to produce a suitable binding stitch along one side of the line; and when the top of the slot is reached, the sewing machine is reversed and a suitable binding is then run along the other side of the line until a complete binding is obtained.
It is necessary for the operator to observe when the binding has been made along the entire length of the slit and to, at that point, move the fabric over and reverse the sewing machine to complete the binding. When many buttonholes of the same size are to be made, it is not necessary to mark the length of each buttonhole on the fabric because buttonhole attachments ordinarily have a rough scale along one rail that can be used to guage the length of the hole.
Since buttonholes ordinarily are placed in finished articles, it is extremely important that the buttonholes be the right length for the button being used. Buttonholes of the wrong size may be very wasteful and may require remaking the entire buttonhole if it is too small, obtaining larger buttons if the buttonholes are too large, or in extreme cases wasting an already made article.